"My concerns are, do I still have something to give, and when is it going to jump the shark?"

Oh for Pete's sake! Someone out there give that woman my email address because I want to give her a piece of my mind. This is no time for her to give up now. I've already established that Buffy the Vampire Slayer has Jumped The Shark a dozen times over and it doesn't matter. The show is immune to Shark Jumping. It's the living exception to the rule. Technically it jumped the shark when it jumped out of the gate, so that's a completely irrelevant reason to give up the ship.

If she really felt these were the best people she's ever known, and the job was the best job she's ever had, she'd fight to keep it. My guess is she's buckling under the pressure of all those idiots who blabber that she's the reason season six wasn't whatever the hell they wanted. Well I for one think she's done a fine job, and people who have ill will towards Noxon have said their piece and should now shut the hell up.

I agree with you in many respects, but I suspect she's worried more about the show jumping the shark (reaching a point where it starts a decline in true quality) offscreen than with a particular on-screen story. If the show runs long enough, it's possible the creative team will simply run out of new stories to tell and new things to say. I don't really think that would happen, and it's worth noting that she says as much herself:

"we’d do good work no matter what, because [the BUFFY team are] some brilliant and fantastic people. We’re all very happy at our jobs, and that’s such a rarity in Hollywood. So you can’t discount that, either."